Conventionally, various systems for controlling an engine of a vehicle to automatically control the running speed of the vehicle have been provided. Such control may be constant speed running control, accelerated or decelerated running control or the like. Those systems are provided principally in order to facilitate operation for running of a vehicle. For example, it is anticipated to attain desired running of a vehicle with minimized operations of an accelerator pedal or a brake pedal.
Particularly when a vehicle is running following another preceding vehicle on a road where traffic is heavy, the running speed must be changed particularly frequently, and it is very important to allow the running speed of the vehicle to be changed frequently with a minimized number of operations.
However, when the running speed of a vehicle in a constant speed running condition is to be changed, it is necessary, with a conventional engine controlling system for a vehicle, to treadle an accelerator pedal or loosen the treadling of the accelerator pedal until a predetermined car speed is reached and then re-set the constant running speed. Also, it frequently happens that it is desired to cause a vehicle to run at a constant speed after the vehicle has been decelerated to a predetermined speed by treadling operation of a brake pedal. In such an instance, normally a conventional engine controlling system for a vehicle is reset each time the brake pedal is treadled, and consequently, it is necessary to re-start constant speed running control by manual operation. Thus, the conventional engine controlling systems for an engine have drawbacks that such operation as described just above makes a burden to the driver and that the essential object of a controlling means of the type to facilitate operation cannot be attained sufficiently.
The present invention has been made in view of such a subject as described above, and it is an object of the present invention to provide an engine controlling system for a vehicle which can attain easy and smooth transition to constant speed running of the vehicle even after operation of a brake pedal or an accelerator pedal and with which a will of a driver for driving can reflect with certainty on running of the vehicle.